Manufacture of alkylated aromatic compounds



Aug. 28, 1962 I E. A. HUNTER ETAL 3,051,765

MANUFACTURE OF ALKYLATED AROMATIC COMPOUNDS Filed April 1, 1960 AROMATlC F o l 2- 'QI 8 VENT RECYCLEI I ETHYLENE REACTOR 'l 4 STR'PPED LIGHT ENDS RECOVERY l 5, l OR RECYCLE TO REACTOR CUMENE FRACTIONATOR RECYCLE H TDDETERGENTALKYLATE l STORAGE PRODUCT l0 -HEAVYALKYLATE STORAGE FlGrl FRACTIONATOR FIG.- 2

IN|ITIATOR REACTANTS FIG.'3

Edward Allen Hunfer Clyde Lee Aldridge lnvenrors Duvid Edward Gensheimer By lbw HM Their Purenl Alrorney nited rates atcnt @tt as 3,05l,700 Patented Aug. 28, 1062 3,051,766 MANUFACTURE OF ALKYLATED ARGIWATIC CGMPUUNDS Edward Ailen Hunter, Clyde Lee Aldridge, and David Edward Gensheimer, Baton Rouge, La, assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Apr. 1, 1960, Ser. No. 19,294 12 Claims. (Cl. 260668) This invention relates to the production of alkylated aromatic compounds by telomerizing a monoolefin with an aromatic compound in the presence of an initiator wherein the initiator is incrementally added to the reaction mixture. The scope of the phase incremental addition will be defined with specificity subsequently. More particularly this invention relates to a novel process for alkylating aromatic compounds in the presence of certain peroxide initiators which are added incrementally throughout the reaction for the purpose of markedly increasing the yield of desired product.

This application is a continuation-in-part of application Serial No. 779,343, filed December 10, 1958, now abandoned.

It has been known that benzene may be alkylated with an alkyl halide to produce alkyl aromatic compounds which are especially suitable for the production of oil and water soluble detergents, i.e., alkylaryl sulfonates. Also benzene has been condensed with long chain olefins or alcohols to obtain the long chain alkyl aromatic compounds also suitable as intermediates in the manufacture of detergents.

Several other techniques for the production of alkylated aromatic compounds are known in the art. More recently there has been discovered a technique for synthesizing higher alkyl aromatic compounds by reacting a low molecular weight mono-olefin such as propylene or preferably ethylene with a lower alkyl aromatic compound, i.e. an alkyl benzene containing 7 to 14 carbon atoms per molecule. Aromatic hydrocarbons containing only a single alkyl substituent per molecule, e.g. toluene or cumene, are especially preferred. According to this technique the reaction is carried out in the presence of an initiator whereby a free radical is established in the aromatic compound, at which point one or more ethylene molecules are added to yield a higher molecular weight alkylated aromatic compound. In such a telomerization reaction the olefin compound in efiect grows as an alkyl chain onto the aromatic compound attaining molecular weights of 1500 and higher. Thus, while it is possible to start with a relatively long chain alkyl benzene such as dodecyl benzene to obtain still higher molecular weight alkylated aromatic compounds, usually there is little economic incentive for employing alkyl benzenes having over eight carbon atoms in the alkyl chain.

In this latter technique, there have been employed as initiators, various sources of free radicals such as cumene hydroperoxide, tetralin hydroperoxide, hydrogen peroxide, ditertiary butyl peroxide, tertiary butyl hydroperoxide, benzoyl peroxide, bis-Z-phenylpropyl peroxide-2, sodium peroxide, acetyl peroxide, tertiary butyl peracetate, potassium persulfate, a,a'-azodiisobutyronitrile and similar compounds. Peroxides containing no atoms other than oxygen, hydrogen and carbon, and cumene hydroperoxide in particular, are preferred.

It has now been found that alkylated aromatic compounds in markedly higher yields than have been previously obtained can be prepared by reacting an aromatic compound with a low molecular weight mono-olefin at temperatures of 100 to 350 C. and preferably 200 to 300 C. at atmospheric or elevated pressures, e.g. at 500 to 5000 p.s.i.g. and higher, in the presence of from 0.1 to 20 grams of initiator per liter of aromatic feed. As the aromatic compound, there may be employed toluene, the various xylenes, cumene, ethylbenzene, heptylbenzene or various other alkylated aromatic hydrocarbons. As indicated earlier, monoalkylated benzene hydrocarbons having an alkyl chain of less than about 8 carbon atoms are preferred when it is desired to make detergent grade alkylates. Polynuclear aromatic compounds such as naphthalene and alkylated naphthalenes as well as polyalkylated benzenes such as the several xylenes are also suitable for this reaction when the corresponding products are desired for special purposes. If desired, a mixture of two or more of these aromatic compounds may be employed as feed stock.

Preferably, ethylene is employed as the mono-olefin at pressures of 50C- to 2000 p.s.i.g., although as previously indicated, this reaction may be effected at atmospheric to extremely high pressures of, for example, 5000 p.s.i.g. Usually the higher pressures, which will effect an increase in ethylene solubility, will result in increased yield and higher average molecular weight product. Insofar as the temperature is concerned, it is preferred to maintain the reaction mixture at temperatures substantially higher than that at which the initiator employed has a substantial decomposition rate, and preferably to 250 C. higher than the decomposition temperature of the initiator. For instance, cumene hydroperoxide shows extensive decomposition at 50 C. and higher while hydrogen peroxide shows strong decomposition at temperatures of C. and above. The initiator is maintained at temperatures below its decomposition temperature prior to its entry into the reaction mixture. The initiator, upon contact with the reaction mixture which is maintained at the aforesaid elevated temperatures, decomposes rapidly.

it is advisable to maintain the initiator below its decomposition temperature up to the time of introduction to the reactor so that no initiator is lost by decomposition prior to contact with reactants. Maintaining the reactor temperature at a level substantially higher than the decomposition temperature of the initiator is an important part of this invention. This technique results in improved initiator efiiciency (higher yield of product per weight of initiator). Although the reason for this improvement is not clear, it is theorized that the heat made available supplies the activation energy required by the chain propagation step.

If desired, the initiator compound may be dissolved in an inert diluent or in liquid reactant for convenience and safety. The reaction time will depend on various circumstances including pressure, temperature, amount of initiator employed and the like. In any event, the products recovered from this telomerization process will include unreacted feed as well as alkylated aromatics having from 3-100 or more carbon atoms in the side chain. The reaction under the preferred conditions set forth herein will yield predominantly an alkylated aromatic having a single long side chain making the product especially useful as an intermediate for detergent production. 7

As previously noted, a critical part of this invention resides in the incremental addition of the initiator to the reaction mixture. This may be defined in terms of a maximum initiator concentration per liter of feed charged at any given time. Thus, incremental addition in a batch operation, wherein the aromatic compound in liquid form is contacted with ethylene under pressures at elevated temperatures and the mixture is continuously agitated, would include adding the total initiator required in two or more increments over the duration of the reaction. These incremental initiator additions must be separated as specified in a later portantamount to adding the initiator in a single batch and is not in accord with the scope of this invention. However, the continuous reaction system may be modified to provide incremental addition of the initiator by recycling a portion of the reaction product mixture to the feed inlet. This permits contact of the reaction product mixture With the initiator for at least a second time. With this recycle technique in such a continuous operation, it becomes apparent that a recycle to fresh feed ratio of X :1 will be equivalent to the use of X-l-l incremental additions assuming continuous injection or addition of initiator with the fresh feed. If desired, the product mixture may be fractionated and one or more fractions recycled in lieu of or in combination with recycle of the unfractionated product mixture. 7

Another alternate for efiecting incremental addition of the initiator comprises a series of reactors wherein the initiator and feed are continuously passed through a first reactor under reaction conditions and the mixture is then passed through a second reactor, or second zone in the same reactor, where additional initiator is added.

Still another alternate for effecting incremental addition of the initiator comprises a long tubular reactor or pipe having means for introducing initiator at intervals along the length of the reactor. To conserve space, the tubular reactor may be of serpentine or sinusoidal configuration. By suitable sizing of the reactor, spacing of the initiator introducing means, and control of the flow rate of reactants through the reactor, incremental initiator may be effected at intervals of 0.5 to 60 minutes, preferably 21 to 15 minutes.

By any of these techniques, incremental addition of the initiator is accomplished to effect high yields of desired product. By contrast, if the initiator is added all at once, it decomposes all at the same time so that the reaction then stops or at least slows down at an excessively high rate.

To demonstrate the eifectiveness of incremental inicremental initiator addition, reference is now had to the following examples wherein the first shows the etfect of a single addition of initiator; Example 2 shows the effect of four incremental initiator additions; and Example 3, ten initiator additions in the system cumene-ethylenecumene hydroperoxide.

Example 1 500 ml. cumene were charged to a one-liter stirred autoclave and the system pressured with ethylene to an equilibrium pressure of 200 p.s.i.g. at 28 C. The mixture was then heated to -260 C. and 0.73 gram cumene hydroperoxide added to the reactor in one batch. Pres- Example 2 Example 1 was repeated using four incremental additions at 15 minute intervals. There was obtained 28.2 grams product per gram initiator.

Example 3 Example 1 was repeated using ten incremental additions at 15 minute intervals. There was obtained 30.7 grams product per gram initiator.

The initiator may be added in more than ten incre of cumene.

reaction conditions.

1. ments if desired without any detrimental effects as long as such increments are suitably spaced in time. However, normally the use of more than about ten to twelve increments will result in only trifling improvement in initiator efiiciency over that obtained with ten to twelve additions.

To show the efifect of temperature in combination with incremental addition on product yield, the following three runs were carried out holding all conditions constant with exception of the temperature.

Example 4 Five hundrel ml. of cumene were charged to a oneliter stirred autoclave and pressured with ethylene to 200 p.s.i.g. at 28 C. The autoclave was then heated to C. 0.73 gram cumene hydroperoxide in 10 ml. cumene was added to the reactor in ten l-ml. increments at 15 minute intervals. The reaction product mixture was then cooled, the gas vented and unreacted material distilled from the product to 200 C. pot temperature and about 165 C. vapor temperature. There Were recovered as bottoms 4.3 grams of cumene-ethylene telomer of 181 average mol. weight. Only fair initiator .efliciency was obtained as indicated by a yield of 5.9 weights of product per weight of initiator.

Example 5 Example 4 was repeated at 200 C. temperature. 9.5 grams of the cumene-ethylene telomer per gram of initiator were recovered. The initiator efficiency was much improved.

Example 6 Example 4 was repeated at a 225 temperature. 16.5 grams of the cumene-ethylene telomer per gram of initiator were recovered. The initiator efficiency was further improved.

Example7 Example 8 Example 7 was repeated employing ethylbenzene in place of cumene. There was obtained 10.3 weight product per weight initiator, Molecular weight of product=157.

' Example 9 Example 7 was repeated employing toluene in place There was obtained 25.6 grams product per gram initiaton. Molecular weight of product=186.

With regard to incremental addition of initiator in order to obtain increased yields, it is preferred to maintain the concentration of the initiator in the product mixture at approximately less than 50 percent of the total initiator employed and preferably less than about 20% of the total initiator. This range, i.e. less than 50% concentration, will include the use of two or more initiator additions of equal quantity, since if 50% of the initiator is added initially, by the time the second increment also equaling 50% is added, the initially added initiator will have substantially decomposed under the Preferably a total of l to 10 grams of initiator per liter of charge will be, employed with a maximum instantaneous initiator concentration of 5.0 grams per liter of feed. As stated earlier, the increments are added at intervals of 0.5 to 60 minutes, preferably 1 to 15 minutes.

The above examples demonstrate the efiect of incremental initiator addition employing a batch process. For an example of this invention as it relates to a continuous process, reference is now had to FIGURE 1 which depicts a flow diagram of the telomerization process.

In FIGURE 1, reactor E. may be of any conventional type suitable for liquid-vapor phase continuous reactions. Typically this reactor may be in the form of a tube wherein the reactants flow downstream from left to right. The aromatic reactant of the type disclosed earlier, e.g. cumene, is fed in liquid phase into reactor 1 via line 2. Ethylene is also admitted into the reactor preferably under a pressure of up to 5000 p.s.i.g., e.g. 700 p.s.i.g., via line 3. Temperatures within the reactor are preferably maintained between 200 to 300 C. At the same time the initiator, e.g. cumene hydroperoxide, is fed into the reactor via line 4, the initiator is being added at a rate of 0.1 to grams per liter of aromatic feed. If desired, the ethylene, aromatic feed and initiator may be added via the same inlet port. In the continuous process such as that noted in FIGURE 1, the throughput rate may vary between 0.5 to 5 volumes of liquid per volume of reactor per hour (v./v./hr.) so that the actual residence time of the reaction mixture within the reaction zone and under reaction conditions is between 0.2 to 2 hours. The entire reaction product mixture is taken from reactor 1 via line 5 and passed into fractionator 6 wherein unreacted ethylene is purged via line 7. At least some of the ethylene may be recycled via line 8 t0 the reactor. Unreacted aromatic feed, e.g. cumene, is separated from the fractionator via line 9 and may be recycled directly to the reactor via line 2. Some of the cumene may be removed by a line not shown and converted to the hydroperoxide by oxidation with air in an otherwise well-known manner. This cumene hydroperoxide is suitable for use as the initiator.

The main product which may be removed as a lower side stream or as a bottoms fraction from tower 6 is passed via line 10 to a second fractionator 11 wherein the various end products are separated in accordance with their boiling points. For example, the light ends comprising alkylated aromatics having less than about 8 carbon atoms in the alkyl groups may be recovered via line 12 and used for whatever purpose desired. In some cases these lower molecular weight alkyl aromatics may be recycled to the telomerization reactor 1 for further reaction with ethylene. 'Ihose alkylated aromatics in the detergent alkylate range, i.e. having alkyl groups of from 8 to 20 carbon atoms after recovery via line 13 may be converted to water soluble detergents by any of the well-known sulfonation techniques. Heavier alkylated aromatics are removed via line 14 and these are suitable for the production of oil soluble detergents. The latter compounds generally have more than 20 carbon atoms in the side chain. It is to be understood, however, that end products may be separated as desired and in some cases a mixture of lower molecular weight and higher molecular weight alkylated aromatics may be employed as such.

To efifect the incremental initiator addition, the entire reaction product mixture may be recycled to the reactor via line 15 at the ratios noted below. Thus, for example, it one volume of product mixture is recycled per volume of fresh feed, this will amount to two incremental additions of initiator. It is contemplated to employ a recycle of from 1 to volumes of product mixture per volume of fresh feed. Alternatively, fractions of the product mixture may be recycled to effect the desired molecular weight product. Thus, only light ends such as those recovered via line 12 either alone or together wtih aromatics recovered via lines 9, 13 and 14 may be recycled to elfect the incremental addition of the initiator.

Figure 2 represents another embodiment adapted for continuous operation of a telomerization process in accordance with this invention. In the embodiment of FIGURE 2, there are shown three reactors in series, 51, 52 and 53, all being similar to reactor 1 in FIGURE 1. The feed and initiator are admitted via line 54, which as noted previously may represent two or three lines, and passed through reactor 51 under conditions similar to those given for reactor '1. The product mixture leaving reactor 51 via line 55 is passed to reactor 52, wherein it is contacted with additional initiator admitted via line 56. The product mixture from this reactor is then passed via line 57 and the process is repeated in reactor 53 with additional initiator being added via line 58. If desired, olefin concentration may be maintained by injection of additional olefin into each subsequent reactor. The residence time in each reactor, i.e. the interval between incremental initiator additions is in the range of from 0.5 to 60 minutes, preferably 1 to 15 minutes. The cumulative residence time in all three reactors may be between about 0.2 and 2. hours, e.g. 40 minutes. The final product mixture recovered via line 59 is fractioned in tower 60 into the desired fractions. According to this embodiment there may be employed two or more reactors in series to efiect the desired result.

Still another embodiment employing a serpentine reactor 51 and spaced initiator jets 56 is shown in FIG- URE 3.

It will be understood that the foregoing description of the general nature of the invention and its illustration by various specific examples has been presented mainly for purposes of illustration rather than limitation. Various modifications and alternatives of the described invention can be devised by those skilled in the art without departing from the scope and spirit hereof as defined in the appended claims.

What is claimed is:

1. A method for producing an alkylated aromatic compound which comprises contacting a low molecular weight monolefinic hydrocarbon with an alkylated aromatic compound in a reaction zone at a temperature between to 350 C. in the presence of a free radical source initiator, said initiator being added to the reaction mixture in increments at intervals of between 0.5 and 60 minutes to effect improved yields of alkyl aromatic compounds, the total amount of initiator thus added being equivalent to about 0.1 to 20 grams of cumene hydroperoxide per liter of aromatic compound fed to the reac tion zone and the maximum instantaneous initiator concentration being maintained at less than 50 percent of the total initiator employed.

2. A process for preparing a higher alkylated benzene which comprises reacting a monoalkylated benzene of 7 to 14 carbon atoms with ethylene in an enclosed reaction zone at a temperature between 100 to 350 C. and a pressure between 500 to 5000 p.s.i.g. in the presence of a peroxide initiator, said initiator being added to the reaction mixture in at least two increments at intervals of between 1 and 15 minutes, the total amount of initiator thus added being in the range of from 1 to 10 grams of initiator per liter of monoalkylated benzene fed to the reaction zone and the maximum instantaneous initiator concentration being at any time not in excess of 5 grams per liter of monoalkyl benzene feed.

3. A process according to claim 2 wherein said initiator is hydrogen peroxide.

4. A process in accordance with claim 2 wherein said initiator is cumene hydroperoxide and its concentration in the reaction mixture is maintained below about 2 grams per liter of feed.

5. A process according to claim 2 wherein the monoalkylated benzene is toluene.

6. A process according to claim 2 wherein the monoalkylated benzene is cumene.

7. A continuous process for the production of alkylated aromatic compounds which comprises continuously supplying to a reaction zone ethylene, a low molecular weight alkylated aromatic compound and a free radical source initiator, maintaining said reaction zone at a temperature between 100 to 350 C. and a pressure between 500 to 5000 p.s.i.g., recovering a product mixture from said reaction zone and recycling at least a relatively low boiling fraction of the reaction product mixture to said react-ion zone in an amoimt'equal to at least that ofthe afresh feed, the total amount of initiator thus supplied being equivalent to about 0.1 to 20 grams of cumene hydroperoxide per liter of aromatic compound fed to the reaction zone, and the residence time of the reaction mixture in the reaction zone under reaction conditions being about 1 to 15 minutes per pass and the maximum instantaneous initiator concentration being maintained at less than 50 percent of the total initiator employed.

8. A process in accordance with claim 7 wherein a portion of the total reaction product mixture is recycled to the reaction zone before fractionation.

9. A process in accordance with claim 7 for making alkylated aromatic compounds of predetermined molecular weight wherein said product mixture is first fractionated into a plurality of fractions of which one fraction has the desired molecular Weight and at least one other fraction has a relatively loW molecular weight, and the last named low molecular Weight fraction of said product mixture is recycled to said reaction zone..

' 10. A process for producing a monoalkylbenzene of 9 to 20 carbon atoms per molecule which comprises continuously feeding ethylene and toluene and a hydrocarbon peroxide initiator into a reaction stage, maintaining said reaction stage at a temperature of 200 to 300 C. and a pressure of 500 to 2000 p.s.i.g., passing said reaction product mixture in series to at least one additional reaction stage maintained within the aforesaid ranges of temperature and pressure, adding fresh increments of initiator to each subsequent reaction stage, and recovering monoalkyl benzene product from the resulting mixture, fresh initiator being added to the processin a total amount between l and 10 grams of initiator per liter of toluene, the incremental additions of initiator *being spaced by inrtervals of between about 1 and 15 minutes from one stage to the next and the maximum instantaneous initiator concentration being maintained at less than percent of the total initiator employed.

11. A- process according to claim 10 wherein said series of reaction stages is in the form of a continuous serpentine tubular zone.

12. A method for producing an alkylated aromatic compound which comprises contacting a low molecular weight mono-olefinic hydrocarbon with an alkylaited aromatic compound in a reaction zone at a temperature between to 350 C. in the presence of a free radical source initiator, said initiator being added to the reaction mixture over a time interval such that the maximum instantaneous initiator concentration in the reaction product mixture formed is maintained at less than about 50% of :the total initiator employed.

References Cited in the file of this patent UNITED STATES PATENTS 2,660,610 Erchak Nov. 24, 1953 

1. A METHOD FOR PROCUING AN ALKYLATED AROMATIC COMPOUND WHICH COMPRISES CONTACTING A LOW MOLECULAR WEIGHT MONOLEFINIC HYDROCARBON WITH AN ALKYLATED AROMATIC 